1. Field of the Invention
This invention relates to a fluid level monitor having an ultrasonic transducer that is adapted to accurately detect the level of oil or water in a storage tank of the kind that is typically located in the field near an oil or gas well. The monitor includes an explosion proof casing and wireless transmission means by which fluid level data is sent to a remote mobile or stationary data collector or relay.
2. Background Art
It is desirable to be able to monitor the level of oil (or water) that is removed from an oil (or gas) well and stored within a recovery tank near the well. Accurate monitoring is required to reduce the risks of an overflow condition and potential oil spillage at the tank site which could result in an environmental and/or safety hazard. One conventional technique to accomplish such oil level monitoring is for a workman to go out in the field and drive from tank-to-tank. The workman climbs to the top of each tank, and a string or similar line is then dropped into the tank from above to measure the oil level. The workman manually records the oil levels of the tanks and then returns to his base of operation. The aforementioned technique of having to visit the tanks in the field on a one-by-one basis at which to use a string test line and make a manual record of the oil levels is very time consuming, expensive and not completely accurate. Moreover, the monitoring procedure is completed at relatively long intervals, such that a tank approaching full capacity may not be detected in time to avoid an overflow.
Ultrasonic tank level monitoring methods are known. However, such ultrasonic methods tend to be inaccurate because they fail to take into account the environment within the tank in which the level measurements are to be taken. For example, temperature and pressure changes within the tank, surface ripples, a short measurement range to the surface of the oil, and hydrocarbon vapors which fill the tank above the oil may all give rise to false readings and an indication of more or less oil than is actually present. In addition, conventional ultrasonic monitoring methods are typically limited to tanks which are no greater than twelve feet high. Moreover, few ultrasonic tank level monitors are capable of transmitting data by wireless transmission means. In this regard, the level data is often transmitted over wire lines which mandates an independent source of power, increases the cost of installation and maintenance, and limits the rate and range at which data can be transmitted. Furthermore, a costly vapor tight conduit running above the tank is also required to surround and protect those wires which transmit the oil level data.
The environment in which the tank level measurements are taken is known to be very hostile and corrosive. More particularly, the environment inside and surrounding an oil storage tank is typically acidic, includes a high concentration of potentially volatile vapors, and is subject to temperature extremes which often range from as low as −30 degrees C. to as high as +60 degrees C. Workmen who must enter the hazardous environment of an oil well and its neighboring storage tank to collect or receive oil level data are exposed to personal risk. In this same regard, there is no known ultrasonic tank level monitoring equipment currently in use that is both gas tight and explosion proof so as to ensure the ability of the monitoring equipment to function properly in such a hostile environment.
Accordingly, it would be desirable to have a low maintenance, battery powered ultrasonic oil level monitor that is encased in a gas tight/explosion proof casing which can be quickly and easily coupled to a storage tank and that is adapted to transmit highly accurate oil level data to a location outside the explosive environment of the tank by low power wireless means so as to avoid the problems and inherent risks that have heretofor been associated with conventional oil tank level monitors and data transmission techniques.